This invention relates to a blower as used in a vacuum cleaner or the like and in particular to a diffuser of the blower.
In a vacuum cleaner, air is moved to pick up dirt, dust and debris and deliver it to a dirt container, usually in the form of a filter bag supported within a canister. To cause the air flow, a blower is used to create a vacuum. Hence, the blower is also known as a vacuum motor or vacuum cleaner motor.
The blower motor comprises a motor, typically an electric motor and of the electric motors, universal motors are commonly preferred although PMDC motors and brushless DC motors, switched reluctance motors and induction motors have been used. Generally, universal motors are preferred for domestic applications due to the lower cost and good reliability features but recently also because of their ability to operate at higher speeds in excess of 20,000 rpm, sometimes even greater than 40,000 rpm. The trend towards high speeds which allows the size of the motor to be reduced while keeping the volume of air flow and/or maximum suction high making the overall weight of the vacuum cleaner lighter.
The motor drives an impeller which creates the air flow. The impeller is fitted to the shaft of the motor and has a cover which defines the suction inlet or inlet port for the blower. A diffuser plate guides the air from the impeller through the motor where it is exhausted through openings in the motor housing after cooling the motor. This type of construction is known as a flow-through construction as the air flows through the motor. The alternative construction is known as a bypass construction, as the air bypasses the motor. This type of construction is used in wet and dry type vacuum cleaners.
The construction of the diffuser is very important as it affects the efficiency of the blower. A highly efficient diffuser can increase the volume of air being moved or reduces the power required to move the same volume of air. Hence, as the trend for smaller, lighter motors continues, the desire for a more efficient diffuser is obvious.
One such diffuser development is described in EP0602007 where the relationship between the impeller and the diffuser is investigated with the result that the vanes on the diffuser which surround the impeller, should have an inlet angle, that is the angle that a diffuser vane makes with a tangent to the impeller, of between 1° to 4°.